The point of the article is that is more than one path to the mainstream beliefs on climate change.

If you have a single path of research that leads to a conclusion then you have a valid but relatively weak conclusion. But if you have five separate paths of research all leading to the same conclusion then you have a much stronger case. The article claims there are many such independent paths to the mainstream conclusions on climate change. It also concludes that the skeptics do not have even a single path of research that leads to position of the skeptics.

It is like evolution. You can conclude evolution from just comparative biology. But you can also get the same conclusion from genetics. They are independent of each other as research paths but give the same answer. That increases confidence in the conclusion.